unfortunately, yes, (for some) being overweight can effect your chances of conceiving.
Can weight impact your ability to get pregnant? - Health - MSNBC.com
Personally, I'm glad my doctor never mention to me that I was overweight and needed to lose weight before I started trying to conceive. I have some friends that are OBESE and became pregnant w/ injections and then there are my other friends overweight and still trying to conceive.
I couldn't imagine myself being overweight and then adding in a pregnancy.